JavaTM 2 Platform
Std. Ed. v1.3.1

java.security
Class KeyPairGenerator

java.lang.Object
  |
  +--java.security.KeyPairGeneratorSpi
        |
        +--java.security.KeyPairGenerator

public abstract class KeyPairGenerator
extends KeyPairGeneratorSpi

The KeyPairGenerator class is used to generate pairs of public and private keys. Key pair generators are constructed using the getInstance factory methods (static methods that return instances of a given class).

A Key pair generator for a particular algorithm creates a public/private key pair that can be used with this algorithm. It also associates algorithm-specific parameters with each of the generated keys.

There are two ways to generate a key pair: in an algorithm-independent manner, and in an algorithm-specific manner. The only difference between the two is the initialization of the object:

In case the client does not explicitly initialize the KeyPairGenerator (via a call to an initialize method), each provider must supply (and document) a default initialization. For example, the Sun provider uses a default modulus size (keysize) of 1024 bits.

Note that this class is abstract and extends from KeyPairGeneratorSpi for historical reasons. Application developers should only take notice of the methods defined in this KeyPairGenerator class; all the methods in the superclass are intended for cryptographic service providers who wish to supply their own implementations of key pair generators.

See Also:
AlgorithmParameterSpec

Constructor Summary
protected KeyPairGenerator(String algorithm)
          Creates a KeyPairGenerator object for the specified algorithm.
 
Method Summary
 KeyPair generateKeyPair()
          Generates a key pair.
 KeyPair genKeyPair()
          Generates a key pair.
 String getAlgorithm()
          Returns the standard name of the algorithm for this key pair generator.
static KeyPairGenerator getInstance(String algorithm)
          Generates a KeyPairGenerator object that implements the specified digest algorithm.
static KeyPairGenerator getInstance(String algorithm, String provider)
          Generates a KeyPairGenerator object implementing the specified algorithm, as supplied from the specified provider, if such an algorithm is available from the provider.
 Provider getProvider()
          Returns the provider of this key pair generator object.
 void initialize(AlgorithmParameterSpec params)
          Initializes the key pair generator using the specified parameter set and the SecureRandom implementation of the highest-priority installed provider as the source of randomness.
 void initialize(AlgorithmParameterSpec params, SecureRandom random)
          Initializes the key pair generator with the given parameter set and source of randomness.
 void initialize(int keysize)
          Initializes the key pair generator for a certain keysize using a default parameter set and the SecureRandom implementation of the highest-priority installed provider as the source of randomness.
 void initialize(int keysize, SecureRandom random)
          Initializes the key pair generator for a certain keysize with the given source of randomness (and a default parameter set).
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

KeyPairGenerator

protected KeyPairGenerator(String algorithm)
Creates a KeyPairGenerator object for the specified algorithm.
Parameters:
algorithm - the standard string name of the algorithm. See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard algorithm names.
Method Detail

getAlgorithm

public String getAlgorithm()
Returns the standard name of the algorithm for this key pair generator. See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard algorithm names.
Returns:
the standard string name of the algorithm.

getInstance

public static KeyPairGenerator getInstance(String algorithm)
                                    throws NoSuchAlgorithmException
Generates a KeyPairGenerator object that implements the specified digest algorithm. If the default provider package provides an implementation of the requested digest algorithm, an instance of KeyPairGenerator containing that implementation is returned. If the algorithm is not available in the default package, other packages are searched.
Parameters:
algorithm - the standard string name of the algorithm. See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard algorithm names.
Returns:
the new KeyPairGenerator object.
Throws:
NoSuchAlgorithmException - if the algorithm is not available in the environment.

getInstance

public static KeyPairGenerator getInstance(String algorithm,
                                           String provider)
                                    throws NoSuchAlgorithmException,
                                           NoSuchProviderException
Generates a KeyPairGenerator object implementing the specified algorithm, as supplied from the specified provider, if such an algorithm is available from the provider.
Parameters:
algorithm - the standard string name of the algorithm. See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard algorithm names.
provider - the string name of the provider.
Returns:
the new KeyPairGenerator object.
Throws:
NoSuchAlgorithmException - if the algorithm is not available from the provider.
NoSuchProviderException - if the provider is not available in the environment.
See Also:
Provider

getProvider

public final Provider getProvider()
Returns the provider of this key pair generator object.
Returns:
the provider of this key pair generator object

initialize

public void initialize(int keysize)
Initializes the key pair generator for a certain keysize using a default parameter set and the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness is used.)
Parameters:
keysize - the keysize. This is an algorithm-specific metric, such as modulus length, specified in number of bits.
Throws:
InvalidParameterException - if the keysize is not supported by this KeyPairGenerator object.

initialize

public void initialize(int keysize,
                       SecureRandom random)
Initializes the key pair generator for a certain keysize with the given source of randomness (and a default parameter set).
Overrides:
initialize in class KeyPairGeneratorSpi
Parameters:
keysize - the keysize. This is an algorithm-specific metric, such as modulus length, specified in number of bits.
random - the source of randomness.
Throws:
InvalidParameterException - if the keysize is not supported by this KeyPairGenerator object.
Since:
1.2

initialize

public void initialize(AlgorithmParameterSpec params)
                throws InvalidAlgorithmParameterException
Initializes the key pair generator using the specified parameter set and the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness is used.).

This concrete method has been added to this previously-defined abstract class. This method calls the KeyPairGeneratorSpi initialize(java.security.spec.AlgorithmParameterSpec, java.security.SecureRandom) initialize method, passing it params and a source of randomness (obtained from the highest-priority installed provider or system-provided if none of the installed providers supply one). That initialize method always throws an UnsupportedOperationException if it is not overridden by the provider.

Parameters:
params - the parameter set used to generate the keys.
Throws:
InvalidAlgorithmParameterException - if the given parameters are inappropriate for this key pair generator.
Since:
1.2

initialize

public void initialize(AlgorithmParameterSpec params,
                       SecureRandom random)
                throws InvalidAlgorithmParameterException
Initializes the key pair generator with the given parameter set and source of randomness.

This concrete method has been added to this previously-defined abstract class. This method calls the KeyPairGeneratorSpi initialize(java.security.spec.AlgorithmParameterSpec, java.security.SecureRandom) initialize method, passing it params and random. That initialize method always throws an UnsupportedOperationException if it is not overridden by the provider.

Overrides:
initialize in class KeyPairGeneratorSpi
Parameters:
params - the parameter set used to generate the keys.
random - the source of randomness.
Throws:
InvalidAlgorithmParameterException - if the given parameters are inappropriate for this key pair generator.
Since:
1.2

genKeyPair

public final KeyPair genKeyPair()
Generates a key pair.

If this KeyPairGenerator has not been initialized explicitly, provider-specific defaults will be used for the size and other (algorithm-specific) values of the generated keys.

This will generate a new key pair every time it is called.

This method is functionally equivalent to generateKeyPair.

Returns:
the generated key pair
Since:
1.2

generateKeyPair

public KeyPair generateKeyPair()
Generates a key pair.

If this KeyPairGenerator has not been initialized explicitly, provider-specific defaults will be used for the size and other (algorithm-specific) values of the generated keys.

This will generate a new key pair every time it is called.

This method is functionally equivalent to genKeyPair.

Overrides:
generateKeyPair in class KeyPairGeneratorSpi
Returns:
the generated key pair

JavaTM 2 Platform
Std. Ed. v1.3.1

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

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